There are many apparatuses and processes in which gases are used to treat water, including the treatment of water with ozone. As a consequence of this treatment, these processes result in to water which contains unabsorbed gas. The unabsorbed gas in the water then has to be separated out of the water. In particular, in many jurisdictions there are strict regulations as to the maximum amount of unabsorbed gas such as ozone which can be present in the water after treatment. For example, in the pool and spa industry, the unabsorbed ozone gas levels allowed in the water arm strictly regulated.
Many of the prior art devices for removing unabsorbed gases from a liquid have generally been very large devices which involve a degassing tank which is operated at atmospheric pressure. The tank often employs a system of complicated baffles or other structural elements which are used to create turbulence in the mixture. The turbulence facilitates the physical separation of the gas from the liquid. For example, in U.S. Pat. No. 1,055,549 to McIntosh there is described an apparatus for separating gas from liquid wherein the gas is separated from the liquid in an apparatus in which a series of horizontal flanges are placed in a circular fashion around an inlet pipe. The exit to the inlet pipe is placed in the air space above the liquids. As the liquid exits the inlet pipe, it cascades over the flanges creating turbulence in the liquid which facilitates the release of gas from the liquid. The gas is then collected and piped away for further use. The liquid is collected in an overflow pipe.
In U.S. Pat. No. 5,380,471 to Ban et al., an aeration tank for producing ultrapure water is described in which the unreacted/unabsorbed gas is separated from water which has been treated with aeration gas. The gas is separated from the water by passing the water around the bottom and top of vertical partitions which are placed in a tank. The water passes around these partitions creating turbulence causing the gas to separate out of the water.
U.S. Pat. No. 5,302,298 to Leitzke describes a process for treating liquids charged with pollutants which includes treating the liquid with ozone gas. Part of the process includes passing the liquid over walls of a tank by releasing the unabsorbed gas into the air space above the tank which is then drawn out of the vessel through an outlet line.
Other prior art devices have simply incorporated means for venting the unabsorbed gas from a collection chamber containing the mixture of unabsorbed gas and liquid. For example, in U.S. Pat. No. 5,376,265 to Szabo, there is described an ozone/water contactor which includes an off-gas collector. The off-gas collector comprises a housing in which the treated water is collected. Within the housing is a float with a needle valve which operates together with an aperture in the roof of the housing to either close the aperture or vent the unabsorbed gas. As the unabsorbed ozone gas is released into the housing it displaces the liquid. The float with a needle valve moves downwards with the displaced liquid removing the needle valve from the aperture in the roof of the housing. The gas escapes through the aperture. Once the gas is released, the water collects in the housing again causing the float and needle valve to rise blocking the aperture. This housing essentially acts as a collecting and venting chamber. There is no means described in this patent to facilitate the physical separation of the gas from the water.
These prior art devices have failed to effectively remove substantially all of the unabsorbed gases from the liquid. Additionally, the prior art devices are also generally large and cumbersome which make them difficult to use in smaller applications.